Cestodes Tapeworms- are segmented worms- The adults reside in the gastrointestinal tract, but the larvae can befound in almost any organ- Human tapeworm infections can be divided into two major clinicalgroups: In one group, humans are the definitive hosts, the adult tapeworms livein the gastrointestinal tract (Taenia saginata, Diphyllobothrium,Hymenolepis, and Dipylidium caninum). In the other, humans are intermediate hosts, and larval-stage parasitesare present in the tissues.
Echinococcosis Hydatid deseaseEchinococcosis of humans is caused by thelarval stage of Echinococcus granulosus- ECHINOCOCCUS GRANULOSUS GRANULOSUS- ECHINOCOCCUS GRANULOSUS BOREALIS- ECHINOCOCCUS GRANULOSUS CANADIENSIS- ECHINOCOCCUS GRANULOSUS EQUINUSE. granulosus produces unilocular cystic lesions
E. granulosus isprevalent in areaswhere livestock israised in associationwith dogs.E. granulosusis found in:Australia, Argentina,Chile, Africa, easternEurope, the MiddleEast, NewZealand, and theMediterraneanregion, particularlyLebanon and Greece.
E. granulosusis found in:Australia, Argentina, Chile, Africa, easternEurope, theMiddleEast, NewZealand, and theMediterraneanregion, particularlyLebanon andGreece.
Echinococcal species have 2 hosts:• intermediate and• definitive hosts1. Definitive hosts are dogs,that pass eggs in their feces2. Intermediate hosts are:• sheep, cattle, humans, goats,camels, and horses
EtiologyAdult E. granulosus is asmall (2,7-5 mm long) cestode,which lives for 5 to 20 monthsin the jejunum of dogs, чакал, вълк,He has scolex with hookless,only 3-4 proglottids –immature, mature, and gravid (400 — 800 eggs)
After humansingest the eggs,embryos escapefrom the eggs,penetrate theintestinalmucosa, enterthe portalcirculation,and are carriedto organs.The life cycle iscompleted whena dog ingestslamb containingcysts
Larvae develop intofluid-filled unilocularhydatid cysts thatconsist of an externalmembrane and an innergerminal layer.Daughter cystsdevelop from the inneraspect of the germinallayer, as do germinatingcystic structures calledBrood capsules.
Newlarvae,calledscolices,develop in largenumbers withinthe broodcapsule.
Clinical Manifestations1. Slowly enlarging EC generally remain asymptomatic, until their expanding size or their space-ccupying effect in an involved organ elicits symptoms.Since a period of 5 - 20 years EC may be discovered incidentallyon a routine x-ray or US study.2. Rupture can occur: spontaneously or at surgery .Cysts may involve any organ.
DiagnosisRadiographic and related imagingstudies are important in detectingand evaluating echinococcal cysts.X-ray will define pulmonary cysts:- usually as rounded, uniformdensity- but may miss other cysts in otherorgans unless there is cyst wallcalcification (as occurs in the liver).
Pathognomonic finding is: -daughter cyst within the larger cyst. -eggshell or mural calcificationThise findings on CT,is indicative of E.G.invasion and helps todistinguish fromcarcinomas, bacterialor amebic liverabscesses, or hemangiomas.
A specific diagnosis can be madeby:the examination of aspiratedfluids for scoliceal hooklets, butdiagnostic aspiration is notconventionally recommendedbecause of the risk of fluid leakage resulting in either dissemination oranaphylactic reactions.
Serodiagnostic assaysSerodiagnostic methods are:• HAT, positive titres 1: 200• ELISA, positive titres 1: 200• IFA positive titres 1: 20• immunoblotting testSerodiagnostic assays can be a negative(up to 30 % of patients may have negativeresultes), but does not exclude the diagnosisof echinococcosis.
TREATMENT Therapy for echinococcosis is based on considerations of the size, location, and manifestations of cysts and the overall health of the patient.• Surgery, when feasible, is the principal definitive method of treatment; E. granulosus cysts are excised.• Risks at surgery from leakage of fluid include anaphylaxis and dissemination of infectious scolices. The latter complication has been minimized by the instillation of scolicidal solutions such as hypertonic saline or ethanol, which may cause hypernatremia, intoxication, or sclerosing cholangitis.
Chemotherapy• As medical therapy, albendazole, given at a dose of:• 10-15 mg/kg/day for 30 days, with 15 days intervals or• 400 mg twice a day for 12 weeks,is most efficacious, although multiple courses may be necessary• Response to treatment is best assessed by repeated evaluation of cysts by CT or MRI, with particular attention to cyst size and consistency.
PreventionIn endemic areas, echinococcosis can be prevented by:- administering praziquantel to infected dogs every 3 months- by denying dogs access to butchering sites and to the offal of infected animals.- Limitation of the number of stray dogs is helpful in reducing the prevalence of infection among humans.